(define (product sos1 sos2)
    (if (null? sos1)
        `()
        (append
            (product-aux (car sos1) sos2)
            (product (cdr sos1) sos2)
        )
    )
)

(define (product-aux s sos)
    (if (null? sos)
        `()
        (cons
            (cons s (cons (car sos) `()))
            (product-aux s (cdr sos))
        )
    )
)

(display 
    (product `(a b c) `(x y))
)
